Many people suffer from inflammatory bowel disease (IBD). IBD is a generic term used to refer to two inflammatory diseases, ulcerative colitis and Crohn's disease. Ulcerative colitis is a chronic inflammatory disease of unknown etiology that affects various portions of the gastrointestinal (GI) tract, particularly the lower GI tract, and more particularly the colon and/or rectum. Crohn's disease is a serious inflammatory disease of the GI tract. It predominates in the small intestine (ileum) and the large intestine (colon). Various medications are being used to treat inflammatory bowel disease.
It is known to use mesalamine, 5-aminosalicylic acid (5-ASA) to treat ulcerative colitis. While mesalamine may be active in treating ulcerative colitis, it may be absorbed as it passes through the GI tract. This absorption may adversely affect the amount of mesalamine that reaches the lower GI tract, particularly the colon and rectum.
Various mesalamine formulations have been introduced in an attempt to protect mesalamine as it passes through the gut and the upper GI tract. One such formulation is a delayed-release formulation that relies on a pH-sensitive coating surrounding the mesalamine. The coating allows the mesalamine to pass through the gut and upper GI tract without being absorbed so that the mesalamine reaches the target (i.e. the lower GI tract, particularly the colon and/or rectum) intact. In another formulation, mesalamine microspheres surround a mesalamine core. This formulation releases mesalamine throughout the GI tract, rather than targeting the colon specifically. It may be difficult to predict the bioavailability of the various mesalamine formulations when administered to a wide variety of individuals. As a result, it may be difficult to determine the proper dosage for a given individual.
It is also known to use sulfasalazine having the following formula to treat ulcerative colitis. However, sulfasalazine is metabolized in the body to form mesalamine (5-aminosalicylic acid (5-ASA)) and sulfapyridine. Several adverse side affects have been noted from the use of sulfasalazine including nausea, vomiting, abdominal discomfort, and headache to name just a few. These adverse side effects are usually attributed to the activity of sulfapyridine in the GI tract, as well as that absorbed into the system.
U.S. Pat. No. 4,412,992 to Chan proposes mesalamine derivatives. Unlike sulfalazine, the breakdown of these compounds in the intestinal tract may not give rise to undesirable metabolic products. In fact, the non-mesalamine metabolic products may be innocuous.
Olsalazine having the following formula has been used to treat ulcerative colitis. In addition to being relatively expensive to make, olsalazine may have adverse side effects including diarrhea.
It is known to use azathioprine (6-(1-methyl-4-nitoimidazol-5-ylthio)purine) in the treatment of inflammatory bowel disease. Azathioprine has the following chemical structure: 
It is also known to use 6-mercaptopurine, a metabolite of azathioprine, to treat inflammatory bowel disease. 6-mercaptopurine has the following chemical structure: 
Methotrexate (L-4-amino-N10-methylpteroyl-glutamic acid) has also been used to treat inflammatory bowel disease. Methotrexate has the following chemical structure: 
The polypeptide cyclosporine, which has traditionally been given to transplant patients to prevent organ rejection, has also been used to treat inflammatory bowel disease. The use of cyclosporine to treat IBD may be limited, however, by the various side effects associated with this medication. These side effects include high blood pressure, kidney damage, tremors, headaches, seizures, excessive hair growth, excessive gum growth, confusion, coma, and gout.